This project uses participants in the Baltimore Longitudinal Study of Aging (BLSA) to gain insight into the biochemical and molecular mechanisms underlying age-associated changes in human immune function. Recent data suggests that human T lymphocytes activated through different cellular pathways display distinctive patterns of protein phosphorylation, cytokine synthesis and gene expression, only some of which are age-affected. With increasing age, an increasing large proportion of T-cells undergo cytokine-mediated apotosis.